Why did Global Texture Coordinate disappeared in Blender 2.80?
The global coordinates where an option that only existed for the Blender Internal render engine. 


  Global
  
  The scene’s global 3D coordinates. This is also useful for
  animations; if you move the object, the texture moves across it. It
  can be useful for letting objects appear or disappear at a certain
  position in space.


It wasn't and isn't an option in Cycles or Eevee. The closest equivalent would be the Camera output of the Texture Coordinate node.


  Camera
  
  Position coordinate in camera space.